EP3519623B1

EP3519623B1 - Environmentally friendly method for local and reproducible bleaching of fabric with ozone

Info

Publication number: EP3519623B1
Application number: EP17784899.1A
Authority: EP
Inventors: Christian Bruno SCHIMPER; Paul Sebastian PACHSCHWÖLL; Hubert HETTEGGER
Original assignee: Acticell GmbH
Current assignee: Acticell GmbH; Jeanologia SL
Priority date: 2016-10-03
Filing date: 2017-10-03
Publication date: 2022-06-01
Anticipated expiration: 2037-10-03
Also published as: EP3519623B8; CN110073054A; ES2922545T8; ES2922545T3; PT3519623T; CN110073054B; WO2018065388A1; EP3519623A1

Description

Field of the Invention

The present invention relates to an environmentally friendly method to improve the treatment for changing the color and tone of a dyed fabric. It is related to a method for increasing the bleaching intensity and improving the reproducibility of ozone bleaching of dyed fabrics by an environmentally friendly aqueous ozone booster, which also ensures time stability of the achievable bleaching effect during dwelling of the textile before ozone treatment.

Background Art

Industrial methods for bleaching of jeans and for creating the highly desired vintage and distressed/worn look are mostly based on local treatments like sandblasting and handsanding (mechanical treatment) and/or chemical treatment by e.g. potassium permanganate (KMnO₄), and/or subsequent treatments with pumice stones, hydrogen peroxide (H₂O₂), sodium hypochlorite (NaOCI), or other oxidizing agents, which are sprayed locally onto desired areas of the ready garment. Sandblasting, as a very cheap method used in earlier times, was officially banned from production processes due to highly negative impacts on workers' health (silicosis).
Bleaching or generally speaking discoloration & changing the color and tone and thus the mechanical abrasion or chemical destruction of indigo dye is reducing the color of indigo denim. The dark blue fabric turns light blue to white at the respective treated areas. Although by using potassium permanganate similar effects as with the sandblasting technique can be achieved, this method also has a big disadvantage due to the enormous amounts of heavy-metal containing wastewater produced during treatment and subsequent neutralization and washing as well as the hazardous nature of the chemical itself (intrinsic toxicity and probably teratogenic property). KMnO₄ is not just highly oxidizing and corrosive, but also dangerous to the environment and aquatic systems.
This is the reason why the denim industry is desperately looking for an environmentally friendly alternative, avoiding the formation of heavy-metal containing waste and reducing the amount of water, chemicals and energy consumed in the finishing process of jeans. Therefore, there is a great need to overcome environmental issues in jeans manufacture, which is especially true for creating a vintage/used look.
One current alternative is the use of laser technology, in which the jeans fabric is irradiated with a laser beam and thus the indigo dye is destroyed by local burning. However, for achieving a satisfying bleaching effect, two laser treatments with interim washing and drying would be necessary, making this method - in combination with the rather high water consumption during intermediate washing - costly and very time-consuming. A promising alternative with respect to ecologic and economic terms was shown to be ozone bleaching.
US20140068871 discloses a method for decolorizing a dyed denim fabric through a dry ozone process to obtain a decolorized look in the denim fabric. Ozone on the one hand is indeed a rather toxic gas consisting of three oxygen atoms (O₃), on the other hand it is produced directly on-site from ambient air oxygen in closed chambers e.g. via electric discharge (which means it is easily and ubiquitously available), and it is also quickly decomposing again after application, resulting in essential and harmless oxygen. One big advantage of using ozone is that no chemicals are discharged into the environment such as heavy metals, toxic auxiliaries, and high salt freight by any possibly necessary neutralization step etc., and significant amounts of water can be saved during dry ozone treatment.
In one treatment process as described in US20140068871 a whole denim textile product is wetted with water and then bleached with ozone. In another embodiment the dry ozone treatment process includes spraying water to desired areas of the textile product and bleaching with ozone. In a third dry ozone treatment a drum is loaded with denim textile products together with wetted cotton fabric scraps for cross-wetting, followed by ozone treatment.
Although water can be applied locally by spraying as disclosed in US20140068871 , this process is technically hardly feasible in an industrial environment, in which long process steps and waiting times before the actual bleaching definitely lead to intermediate drying out, resulting in uneven, patchy and not reproducible bleaching effects. This is a hitherto unsolved problem for the industry. One has to imagine that it is mandatory to produce several thousand replicates of a certain style in the denim industry, thus reproducibility is a must. Reworking on the other hand is laborious and costly.
Stability of the achievable effects over time even during prolonged dwelling before the actual ozone bleaching treatment is an important precondition; however, this is currently not possible by the sole use of water as an ozone bleaching booster.
Water in this case is the chemical mediator for ensuring strong bleaching: water is dissolving ozone gas to a certain extent, but it is also swelling the cellulosic fibers of the fabric to a certain extent; the dissolved ozone is then diffusing to the bleaching sites on the textile, potential reaction and degradation products such as other reactive oxygen species (ROS) get stabilized by surrounding water and thus the half-life of reactive species is significantly extended, thus rendering the bleaching process working.
JP2004019084A discloses a method for treating a textile material with ozone after moisturizing it with water. In the described process additionally a powdery body or granules consisting of water soluble salt are sprinkled over the pre-wetted textile material before ozone treatment. Said powder or granules adhere non-uniformly and randomly onto convex parts of the surface, in which discoloration is suppressed at the respective areas by absorption of the surrounding moisture. Respective water soluble salts described in this application, for example, are sodium sulfate (Na₂SO₄), calcium chloride (CaCl₂), magnesium chloride (MgCl₂), magnesium sulfate (MgSO₄) etc., including respective anhydrides or hydrates of said salts. In another embodiment alkaline or reducing agents are used to destroy ozone locally, thus preventing discoloration at respective treated areas.
Another type of ozone treatment of textile material is disclosed in WO2012119532A1 . There a method for treating denim jeans by topical abrasion, followed by rinsing with water, ozone treatment and final rinsing with water is described, in which no other chemicals are used in any of the steps except water and ozone. Here initial rinsing is necessary to remove the bulk of sizing and to establish moist conditions, which is essential for successful ozone bleaching action as described above. The bleaching efficiency is depending on critical factors such as moisture level and ozone treatment time, in which a moisture level of 20% (weight of water in relation to weight of denim jeans) gives comparably stronger bleaching than 100% moisture level due to otherwise too high level of free-flowing water; this is also the reason why for example in bleaching of cellulosic pulp in the pulp and paper industry as well as cellulose fiber industry high consistency is desired, as inter alia disclosed in US5181987A . The longer the reaction time the more pronounced the worn and vintage look is. EP554648A discloses a process for decolorizing garments with ozone. Ozone blocking agents are applied before treatment with ozone. WO9513415A and JP-H-061783 are disclosing bleaching of dyed textiles with aqueous bath comprising ozone.
Bleaching of denim and other textile materials in general using ozone technology is well-known and state of the art nowadays as presented above. However, it is still a major challenge to bleach locally and reproducibly in order to achieve desired fading and the modern used/vintage look. So far, on the one hand, mostly the application of a "negative image" by blocking agents is done in order to obtain bleaching only at desired areas. On the other hand either random bleaching or discoloration of the whole textile material and color-adjustment are done. When spraying water as a "positive image" for bleaching a stable and reproducible effect under industrial conditions is impossible due to constantly changing dwelling times and exposure times before the actual ozone treatment of e.g. 60-100 garments in one washing load.
There is still a need for an improved method for this environmentally friendly bleaching method in order to ensure reproducible bleaching treatment of dyed fabric locally and/or over the whole fabric and garment, especially with the focus of time stability of the boosting effect even during prolonged dwelling before the actual bleaching by ozone.

Summary of invention

It is the objective of the present invention to provide for an improved method for creating a vintage or used look on dyed fabric or garments during ozone bleaching.
The object is solved by the subject of the present invention.
According the invention there is provided a method for changing the color of a dyed material such as, for example, cellulosic fiber, yarn, fabric, or garment in order to obtain a vintage or used look, wherein said dyed material is subjected to a pretreatment with a hygroscopic substance and thereafter the dyed material is ozone treated.
According the invention there is provided a method for achieving an unexpected, time stable and reproducible, optionally local, bleaching effect on dyed material by applying ozone (O₃) on a dyed material which has been pretreated by an ozone booster.
The ozone booster is a compound or mixture which enhances the effectiveness of the ozone treatment when compared to water. Preferably, the ozone booster is an environmentally friendly and non-hazardous substance or mixture. In one embodiment the ozone booster comprises at least one hygroscopic substance.
In one embodiment of the invention the method for increasing the color value change of dyed material comprises the following steps:

(a) applying an ozone booster to a dyed material, and (b) dwelling the dyed material of step a) for at least 5 minutes up to 24 hours, or even longer, and (c) applying ozone gas to said dyed material to obtain a change in color intensity.

A further embodiment of the invention relates to a method for increasing the color value change of dyed material comprising the following steps:

(a) mixing at least one hygroscopic substance with water,
(b) applying the mixture to a dyed material, and (c) dwelling the dyed material of step a) for at least 5 minutes up to 24 hours, or even longer, and (d) applying ozone gas to said dyed material to obtain a change in color intensity.

The present application also relates to the use of an aqueous solution comprising at least one hygroscopic substance for increasing the color value change and hue of a dyed material.
The present application further relates to a garment obtained by the inventive method of applying a hygroscopic substance for increasing the color value change of a dyed material by subsequent ozone treatment.

Brief description of drawings

Figure 1: Results of ozone bleaching after pretreatment with samples 1-4 (c.f. Table 1) and water as a reference.
Figure 2: Ozone bleaching after application of different aqueous solutions of hygroscopic substances onto indigo dyed denim textiles.
Figure 3: Bleaching effect by ozone treatment after application onto indigo, sulfur top and sulfur bottom dyed denim textiles.
Figure 4: Comparison of the bleaching effect of an aqueous DMSO solution and pure water as a reference demonstrating stability of the achievable bleaching effect over several hours of dwelling before actual ozone treatment.
Figure 5: Embodiment of the invention, in which an indigo dyed denim fabric was soaked into a solution containing at least one hygroscopic substance. The fabric was then centrifuged, dried and a cover layer comprising a polymer/sizing agent was applied by spraying. The fabric was then dried again. After mechanical abrasion by handsanding the textile was allowed to dwell and then subjected to ozone treatment. Left part: no polymer/sizing agent applied (= reference, whole area bleached due to presence of the hygroscopic substance). Right part: sizing applied, no bleaching at non-scraped area (much higher bleaching effect and strong contrast where sizing had been removed before ozone treatment).

Description of embodiments

The present invention discloses a novel and unexpected combination of an environmentally friendly chemical pretreatment of a dyed material followed by ozone bleaching, in which local and reproducible color value change (c.f. bleaching) effects during a certain time span on the material is achieved. Of particular note is that with the inventive method use of hazardous chemicals like potassium permanganate or chlorine bleaching is avoided.
In industrial processes cotton yarn is subjected to dyeing in order to obtain e.g. the blue color of the later fabric, e.g. denim. In a pretreatment step, so-called mercerization, the yarn is treated with high alkalinity during a short period of time. This treatment is changing the crystalline structure of the cellulose fibers, swelling and shrinking the fibers, and additionally rounding them off. The pretreatment by alkali is responsible for more intense color in the subsequent dyeing step, brighter shades and more ring dyeing as well as superficial dyeing. Traditionally, dyeing of cotton yarn for standard blue denim cotton fabrics is carried out with indigo as the main dyestuff. The second most important dyestuffs are sulfur dyes, which can be applied solely or in combination with indigo in order to create new effects (so-called bottoming or topping with sulfur dye). The way of application is rather similar for both dyestuffs, since from a chemical point of view both dyeing processes are based on oxidation/reduction principles (typical vat dyes). However, due to fashion trends and changing designs and customer needs over the years, colors and used dyestuffs are changing and a posttreatment of the manufactured and dyed jeans is necessary. Here, bleaching of indigo-dyed jeans, which is usually accomplished by oxidative chemical treatment, comes into play and is one of the most used methods for creating the so-called "used" or "vintage look" in the finishing-step of current jeans-manufacture.
Nowadays there are various methods available in the finishing process of the jeans production in order to decolorize dyes, e.g. indigo dye. The bleaching or "used effect" can e.g. be obtained by KMnO₄, chlorine, organic peroxides, persulfates, reducing agents (e.g. glucose), laser treatment, ozone treatment or even by the action of enzymes (e.g. cellulases, laccases, peroxidases). Most of the chemicals used (such as potassium permanganate, PP) are harmful to the environment and hazardous for the respective operators. The industry is thus desperately searching for environmentally friendly and non-hazardous methods with regards to workers safety and health.
Surprisingly, ozone in combination with a chemical pretreatment of the garment with environmentally friendly and non-hazardous chemicals as ozone booster was shown to be a promising alternative to prevailing methods.
Ozone is already used in the jeans industry. Normally it is used for a final clean-up of the garment before the article of clothing is ready for customers, and to adjust the color of the whole garment. This means that there are many ozone-generators/machines available; however, by virtue of the sole use during the clean-up step and color adjustment, the capacities of these machines are usually not fully exploited. So far it was not possible to carry out reproducible local bleaching on e.g. jeans garments using ozone, since the ozone gas is commonly applied to the whole garment. In contrast, potassium permanganate can be applied to the fabric or garment onto very well-defined areas e.g. by spraying, and is thus preferred in terms of reproducibility and local applicability. In existing workflows the garments are stacked in piles and stored temporarily for several hours until the actual ozone treatment is taking place. Thus reproducible and local bleaching has been challenging and an unsolved problem in the denim industry so far, although a great need for non-hazardous alternatives to locally applied PP exists.
US20140068871A1 discloses a method for local jeans bleaching with ozone. The garment is moistened locally in order to be efficiently bleached during ozonation. Only ozone gas which is dissolved in water in turn acts as an effective bleaching agent. However, due to long dwelling times of several hours before ozonation, any moisture applied locally to the jeans is mostly gone, either by drying or random diffusion into the bulk textile.
The present invention overcomes this major disadvantage by using an ozone booster for wetting the garment, which comprises at least one chemical of hygroscopic nature. The ozone booster may inter alia be applied by spraying directly on the dyed material at desired areas, enabling subsequent local ozone bleaching even after prolonged dwelling. The principle of the invention turned out to primarily be based on ensuring a long-lasting and persistent humidity at desired areas of the dyed material, additionally protecting the dyed material against drying due to the special chemical composition of the ozone booster. Only by this it is possible to bleach dyed material reproducibly even after temporary storage.
On the basis of already existing ozone machines and spraying equipment at the factories, the invention can easily be used directly on site with existing equipment and replace environmentally hazardous potassium permanganate spray. Using this new technology, a completely non-toxic ozone booster is in a first step sprayed or applied otherwise directly on desired and selected areas of the dyed material or on the whole garment; the actual bleaching is subsequently carried out in closed ozonation drums e.g. at room temperature without the need of additional water. This process does not burden the health of the employees and the environment.
Moreover, additional positive effects of the presented technology were observed: the amount of water used, e.g. for washing of permanganate-treated denim, is significantly reduced, and no heavy metal waste is emitted into the environment. On the contrary, it is even possible to carry out the washout after ozone treatment solely with cold water, which is indeed sufficient for removing the degradation products of the bleached dye (which are, in case of indigo, for example isatin, isatoic anhydride and anthranilic acid). Thus it is even possible to save several washing cycles at high temperature, additionally saving energy for heating and laundry detergents and/or chemicals for neutralization as in case of potassium permanganate, in which e.g. harmful sodium metabisulfite is mandatory to be used on industrial scale.
For bleaching of dyed material, ozone is a very efficient bleaching agent comprising - due to the chemical structure - high selectivity e.g. towards indigo or sulfur dyes. However, direct destruction of the dye by ozone gas is very limited due to decreased reactivity at the solid/gas interface. A liquid support is thus enhancing the reactivity and bleaching effect significantly. Due to environmental issues in some embodiments an aqueous solution is used as the medium of choice. Under standard temperature and pressure conditions ozone (O₃) is 13 times more soluble in water (570 mg/L = app. 12 mmol/L) compared to regular ambient air oxygen (O₂). This makes water the solvent of choice for ozone bleaching of dyed fabric. In order to obtain a long-lasting wetting effect (up to 6 hours) and prevent drying of the treated areas, different additives have to be used as ozone booster. The most important ones are hygroscopic substances. It was completely unexpected, that the addition of such compounds leads to an increase in bleaching intensity as well as long-term stability and reproducibility of the achievable bleaching effects, since some of these compounds were described in earlier literature as being responsible for even suppressing discoloration by ozone bleaching as disclosed in JP2004019084A (for example CaCl₂, MgCl₂, MgSO₄ or Na₂SO₄). In contrast the inventors of the present invention have found that the substances and compounds disclosed in the present application are positively boosting the bleaching effect of ozone when used under appropriate conditions.
Due to the hygroscopic nature of the ozone booster drying out of treated dyed material is hindered. DMSO, representing a hygroscopic solvent, and further compounds such as an additional swelling agent, may be used in combination with water for swelling of the cellulose fibers, rendering more reactive sites accessible to bleaching and thus enhancing the bleaching effect even more. Besides the composition of the ozone booster, other parameters influencing the bleaching effect are the humidity of the ambient air, the temperature, air pressure, ozone concentration as well as treatment time. High humidity of the ambient air in the factory is prolonging the drying time; the same is true for lower temperatures.
Ozone is produced directly on-site in closed chambers from ambient air after concentration of oxygen followed by electric discharge, according to the following chemical formula:

3 O₂ → 2 O₃
Thus, one embodiment of the invention relates to a method for increasing the color value change of a dyed material comprising the following steps:

(a) applying at least one hygroscopic substance to the dyed material, and
(b) dwelling the dyed material of step a) for at least 5 minutes up to 24 hours, or even longer, and
(c) applying ozone gas to said material to obtain a change in color intensity.

One embodiment of the invention relates to a method for increasing the color value change of a dyed material comprising following steps:

(a) dissolving at least one hygroscopic substance in water,
(b) applying the mixture of step (a) to dyed material, (c) dwelling the dyed material of step b) for at least 5 minutes up to 24 hours, or even longer, and (d) applying ozone gas to said material to obtain a change in color intensity.

Surprisingly it was found that an aqueous solution comprising at least one hygroscopic substance exhibits significant time stability for ensuring proper moistening of the textile surface resulting in significantly enhanced ozone bleaching. This finding is in serious contrast to what has been stated in JP2004019084 , in which certain inorganic salts of hygroscopic nature were claimed to even suppress the bleaching action of subsequent ozone treatment.
In the invention the fabric or garment is dwelled for at least 5 minutes up to 24 hours, or even longer or predried to a certain extent, preferably at room temperature, but also at elevated temperatures, e.g., up to 120°C.
As respective techniques of application of one or more components together or in separate form onto the fabric, yarn or garment, the following techniques well known to a person skilled in the art may be used at any stage of processing, using immersion, padding, spraying, brushing, printing, foaming, sponging, nebulizing, other contact methods like stone and/or powder carrier, kiss roll etc.
In the present invention the term "textile material" or "fabric" are used interchangeably and each refer to fibers, yarns, fabrics, flexible knitted, woven or nonwoven material consisting of a network of natural or artificial fibers (yarn or thread). The textile material may also be used in production of further goods such as cloths, garments, carpets, bags, shoes, jewelry, furnishings, artifacts, etc.
In one embodiment the respective textile material is represented as dyed/colored and finished denim good.
In a further embodiment of the invention the respective material is a textile material represented by a variety of garments including jeans skirts, jeans jackets, jeans shorts, jeans vests, jeans dresses, and/or corduroy and twill garments.
In another embodiment of the invention other cellulosic materials besides denim are treated according to the described methods.
The material may be dyed or coated with a dye, in which the dye may be selected from natural or synthetic dyes of every class; the industry currently preferably uses indigo dye, sulfur dyes and other dyestuff classes (e.g. dischargeable dyes etc.), or combinations thereof as top and bottom blends or mixtures.
The textile material may be of cellulosic origin and selected from natural fibers, such as bast fibers like jute, flax, hemp, leaf fibers such as sisal, seed fibers such as cotton, or bamboo fibers, or man-made fibers such as lyocell fibers, viscose, rayon type fibers, modal, cupro and/or acetate type cellulosic fibers and optionally mixtures with synthetic fibers, if applicable and chemically compatible.
In the invention the fabric or garment is dwelled for at least 5 minutes or up to 24 hours, or even longer if necessary.
In the present invention the term "ozone booster" refers to an environmentally friendly and non-hazardous compound or mixture. Hazardous compounds, such as for example listed in the ECHA database of substances of very high concern, are thus avoided. Suitable non-hazardous compounds are e.g. hygroscopic substances.
The hygroscopic substance may be, but not limited to, selected from the group of hygroscopic inorganic salts, organic compounds, liquids and solvents, alcohols, dicarboxylic and carboxylic acids and deliquescent compounds as well as respective anhydrates or hydrated forms, or mixtures thereof. The hygroscopic compound may be selected from the group, but not limited to, DMSO, aluminum chloride, aluminum nitrate, calcium chloride, calcium nitrate, calcium bromide, carnallite, lithium chloride, lithium bromide, lithium iodide, lithium nitrate, lithium sulfate, magnesium chloride, magnesium nitrate, magnesium sulfate, magnesium bromide, manganese sulfate, tin sulfate, dicarboxylic acids such as malonic acid or oxalic acid, glutaric acid, urea, alpha hydroxy acids such as lactic acid, polyols as for example sorbitol, xylitol, maltitol, glycerol, sodium bromide, sodium sulfate, sodium bisulfate, sodium chloride, sodium nitrate, tachyhydrite, zinc chloride, zinc nitrate, potassium chloride, potassium nitrate, potassium sulfate, potassium bisulfate, potassium bromide, ethanol, methanol, other glycols such as ethylene/propylene/butylene glycol and respective polyglycol derivatives, or mixtures thereof. The list and mode of action is to be extended by any substance comprising hygroscopic behavior, however, due to safety issues and price some compounds such as cadmium nitrate, cobalt chloride, gold chloride, silver perchlorate, sodium bromate, tellurium tetrachloride, thorium nitrate or yttrium chloride may not be feasible for application on an industrial scale.
The concentration of the hygroscopic substance in aqueous solution is typically in the range of 0.1-90 w-%, preferably in the range of 10-80%, more preferably in the range of 20-70 w-%, most preferably in the range of 30-60 w-%, depending on the desired effect. The amount of the hygroscopic substance is solely limited by its respective solubility in water, in which also saturated solutions may be applied, but more preferably the concentration is at least 5-10% below the limit of solubility due to reasons of stability of the solution and the avoidance of unwanted precipitation.
Additionally further textile auxiliary chemicals may be added to the at least one hygroscopic substance in any combination and concentration in solid or liquid form to improve the usability and performance of the said mixture comprising at least one hygroscopic substance and water according to what is required: e.g. dispersants, wetting agents, surfactants, thickening agents, colorants, tinting agents, silicones, leveling agents, antifoams, antimigration agents, antibackstaining agents, softeners, stabilizers, buffer substances, substances for pH adjustment, and optical brightening agents. These additives are well known to persons skilled in the art and can be chosen according to commonly used concentrations depending on the desired effect, e.g., for example in the range of 0.001 to 10%. Further chemicals may be added to impart more desirable improvement of the textile in hand feel or other property like softness, waterproofing, antimicrobial or microbe-reducing chemicals, encapsulated perfumes, etc., or co-solvents (alcohols, ketones, protic solvents, aprotic solvents, polar solvents, apolar solvents, nonionic solvents, ionic solvents, ionic liquids, emulsifying and dispersing agents etc.).
Respective thickening agents may be selected from, but not limited to, compounds which are commonly used as textile auxiliaries, food additives, in cosmetics and personal hygiene products, i.e. starch and modified starches, cellulose and modified celluloses (i.e. methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, hydroxypropylmethyl cellulose, hydroxypropyl cellulose, ethylhydroxyethyl cellulose), alginates (i.e. sodium-, potassium-, ammonium-, propylenglycol alginate), gum arabic, xanthan gum and other natural gums, carrageen, agar-agar, locust bean gum, guar gum, tragacanth, gellan, pectin, gelatin, hyaluronic acid etc. The thickening agent or mixtures thereof may increase the viscosity of the aqueous solution up to 10,000 cP, more preferably up to 1,000 cP, most preferably 100-200 cP, or similar to water.
The solution is preferably an aqueous solution, but it may be also applied separately and stepwise or as at least one pure hygroscopic substance or mixture in powdered or any solid form. In a further embodiment the textile material may also be evenly or unevenly impregnated with said composition using any of the conventional techniques.
In one embodiment of the invention at least one marker dye is added to the aqueous mixture. The marker dye is selected from, for example, but not limited to, acid dyes, azoic dyes like methylene red, basic dyes, dispersing dyes, vat dyes, sulfur dyes and others or food dyes such as for example 8'-Apo-β-caroten-8`-al, Allura Red AC, Aluminum, Amaranth, Annatto (Norbixin), Anthocyane, Azorubin, Betanin, Brillant black, Brillant blue, Brown FK, Brown HT, Canthaxanthin, Capsanthin, Carmoisine, Carotin, Chinolin yellow, Chlorophyll, chromene (e.g. Red, Blue, Yellow), Citrus Red 2, Cochenille red A, Curcumin, Duramine (e.g. Red), Erythrosine, Ethyl-8'-apo-β-caroten-8'-oat, Evron Red, Fast Green FCF, Gold, Green S, Green S, Indigotin, Iron oxide, Lactoflavin, Litholrubin BK, Lutein, Lycopene, Orange B, Patent Blue V, Ponceau 4R, Quinoline Yellow, Riboflavin, Silver, Sunset Yellow FCF, Tartrazine, Titanium dioxide, Xanthene dyes such as Sulforhodamine B or other Fluorescein derivatives, Yellow orange or Zeaxanthin. The marker dye is preferably a food dye.
In one embodiment of the invention the aqueous mixture may further comprise a colorant. The colorant is selected from the same group of dyes as indicated above. The colorant may be added in order to increase the visibility of the aqueous mixture during spraying. The colorant may be added in a concentration in the range of 0.0001 to 10%, preferably in the range of 0.01 to 5%, most preferably in the range of 0.01 to 2%.
In one embodiment of the invention the aqueous mixture may further comprise a wetting agent or surfactant. The wetting agent/surfactant is added for increasing the penetration activity of the aqueous solution. The wetting agent is for example a nonionic or ionic surfactant, most preferably a nonionic surfactant.
In a further embodiment of the present invention, the wetting agent is a mixture of polyglycol ethers of fatty acid alcohols, thus an alcohol alkoxylate. The wetting agent may be added in a concentration in the range of 0.001 to 10%, but more preferably in the range of 0.01 to 5%, most preferably 0.01-1%.
In one embodiment of the invention the aqueous mixture may further comprise a softening agent. The softening agent is for example an anionic/cationic but also a zwitterionic/non-ionic, sometimes silicone-based, surface active compound. The softening agent may be added in a concentration in the range of 0.1 to 25%, or more preferably in the range of 0.1 to 10%.
In one embodiment of the invention the aqueous solution comprises up to 10-95 w-% DMSO.
In one embodiment of the invention the hygroscopic substance containing aqueous solution is applied onto a desized dyed textile.
In another embodiment of the invention the treated textile is subjected to ozone treatment after application of the aqueous solution containing at least one hygroscopic substance. Ozone treatment (ozonation) means contacting the said treated textile with ozone gas in batch or continuous systems. This can for example be done in a washing machine, which is dedicated to ozone washing and thus connected to an ozone generator. The ozonation is typically carried out at room temperature during tumbling of the textile without the use of additional water. New machine types are being recently used or are under development which e.g. apply ozone gas in continuous processes, are suitable as well. The ozonation time is depending on the ozone concentration and ozone production capacity of the respective ozone generator as well as the desired bleaching effect. The lower the ozone concentration, the longer the reaction time for achieving a desired effect is.
In another embodiment of the invention a drum is loaded with denim textile products together with pre-wetted cotton fabric scraps (previously soaked in an aqueous solution comprising at least one hygroscopic substance) for cross-wetting, followed by ozone treatment. This way it is possible to achieve random bleaching enhancement at cross-wetted areas.
In another embodiment of the invention a fabric is soaked into a solution containing at least one hygroscopic substance. The fabric is then dried and optionally a cover layer comprising a polymer coating and/or sizing agent is applied e.g. by spraying, dipping etc. Sizing or coating agents are well-known to a person skilled in the art. The fabric is then dried again. After mechanical abrasion (handsanding) and/or laser treatment the textile is allowed to dwell followed by subsequent ozonized. A contrast will be achieved by the above treatment even if no hygroscopic substance is used. However, the presence of the hygroscopic substance will significantly increase the contrast between the abraded and non-abraded parts of the fabric. The intensity of the contrast between the abraded and non-abraded parts of the fabric is apparent when compared to non-treated fabric.
In a further embodiment of the invention the hygroscopic salt is added to a sizing bath or coating of a yarn. The yarn is then converted into a fabric by e.g. weaving or knitting. After removing the surface coating by means of mechanical abrasion (handsanding) and/or laser treatment etc., the textile is allowed to dwell and subsequently ozonized.
In another embodiment of the invention the hygroscopic salt is applied below the size layer of a yarn or textile.
The key dependent variable in replicating the worn out look is the abrasion intensity, brightness or whiteness of the image. Intensity refers to the purity of a hue. Intensity is also known as chroma or saturation. The highest intensity refers to the purity of a hue. The highest intensity or purity of a hue is the hue as it appears in the spectrum or on the color wheel. A hue reduced in intensity is called a tone.
Color also has a value, i.e. a relative degree of lightness or darkness. Most colors are recognizable in a full range of values; e.g. we identify as a form of "red" everything from the palest pink to the darkest maroon. Even though we assign different names to the different values of red we still know that they are derived from red. All hues have a normal value; the lightness or darkness of that hue as it appears in the spectrum. Yellow, for example, is a light-valued color while violet is a dark-valued color. As a result, there will be an uneven range of light or dark values for each hue.
The color can be measured by means of spectrophotometers and tristimulus colorimeters (Chroma Meters). They measure reflected and transmitted color of objects. These are used in industrial fields and other areas for color quality control, grading by color, and CCM applications on a wide variety of subjects, including automotive parts, paint, plastic, textiles, construction materials and foods, and correcting vision problems.
The measurements are displayed and represented in L*, a* and b* values of the CIE 1976 color space. The L*a*b* color space includes all perceivable colors, which means that its gamut exceeds those of the RGB and CMYK color models. One of the most important attributes of the L*a*b*-model is device independence. This means that the colors are defined independent of their nature of creation or the device they are displayed on. The L*a*b* color space is used when graphics for print have to be converted from RGB to CMYK, as the L*a*b* gamut includes both the RGB and CMYK gamut. Also it is used as an interchange format between different devices as for its device independency. The space itself is a three-dimensional real number space that contains an infinite number of possible representations of colors. However, in practice, the space is usually mapped onto a three-dimensional integer space for device-independent digital representation, and for these reasons, the L*, a*, and b* values are usually absolute, with a pre-defined range. The lightness, L*, represents the darkest black at L* = 0, and the brightest white at L* = 100. The color channels, a* and b*, will represent true neutral gray values at a* = 0 and b* = 0. The red/green opponent colors are represented along the a* axis, with green at negative a* values and red at positive a* values. The yellow/blue opponent colors are represented along the b* axis, with blue at negative b* values and yellow at positive b* values.

Examples

The examples which follow are set forth to aid in the understanding of the invention but are not intended to, and should not be construed to limit the scope of the invention in any way.
A denim garment is treated with an aqueous solution containing at least one hygroscopic substance and subsequently subjected to ozonation.
A denim garment is treated locally with an aqueous solution containing at least one hygroscopic substance and subsequently subjected to ozonation.
A denim garment is treated with sandpaper to roughen parts of the surface and then treated with an aqueous solution containing at least one hygroscopic substance and subsequently subjected to ozonation.
A denim garment is treated locally with an aqueous solution containing at least one hygroscopic substance, allowed to dwell under ambient or elevated temperature conditions for several hours and subsequently subjected to ozonation.
A denim garment is treated with sandpaper to roughen parts of the surface and then treated locally with an aqueous solution containing at least one hygroscopic substance, allowed to dry under ambient or elevated temperature conditions for several hours and subsequently subjected to ozonation.
A denim garment is optionally pretreated with desizing agents, enzymes, chlorine, glucose, peroxides, etc. Then treated locally with an aqueous solution containing at least one hygroscopic substance and subsequently subjected to ozonation.
A denim garment is optionally pretreated with desizing agents, enzymes, chlorine, glucose, peroxides, etc. Then treated locally with an aqueous solution containing at least one hygroscopic substance, allowed to dwell under ambient conditions or elevated temperature conditions for several hours and subsequently subjected to ozonation.
A denim garment is optionally pretreated with desizing agents, enzymes, chlorine, glucose, peroxides, etc., and dried, then treated locally with an aqueous solution containing at least one hygroscopic substance, allowed to dry under ambient or elevated temperature conditions for several hours and subsequently subjected to ozonation.
A whole denim garment is treated with an aqueous solution containing at least one hygroscopic substance and subsequently subjected to ozonation.
A whole denim garment is treated with an aqueous solution containing at least one hygroscopic substance by immersion, then centrifuged and subsequently subjected to ozonation.
A dyed fabric is treated with an aqueous solution containing at least one hygroscopic substance and subsequently subjected to ozonation.
A dyed fabric is locally or one side treated with an aqueous solution containing at least one hygroscopic substance, e.g. by means of printing, spraying, brushing, etc. and subsequently subjected to ozonation.
A dyed yarn is treated with an aqueous solution containing at least one hygroscopic substance by immersion, then coated, dried and processed into a garment and subsequently subjected to ozonation.
A dyed yarn is treated with an aqueous solution containing at least one hygroscopic substance by immersion, then coated, dried and processed into a garment, in which the coating is removed by any means of scraping, lasering, etc. and subsequently subjected to ozonation.
A colored yarn is treated with an aqueous solution containing at least one hygroscopic substance by immersion, then sized, dried and processed into a garment, in which the size is removed by any means of scraping, lasering, etc. and subsequently subjected to ozonation.
A whole denim garment is treated with an aqueous solution containing at least one hygroscopic substance, allowed to dry under ambient or elevated temperature conditions for several hours and subsequently subjected to ozonation.
A material is treated with an aqueous solution containing at least one hygroscopic substance, allowed to dry and then dyed and then subjected to ozonation.
The color changing effect in such pretreated denim garments is generated by subsequent ozonation.
The said aqueous solution comprising at least one hygroscopic salt is applied either by brushing, foaming, immersion, padding, printing, sponging, nebulizing, spraying, or by other methods such as stone and/or powder carrier (contact method).
The treated garment is ozonized directly or after drying/dwelling or storage for several hours - like during common production conditions in the industry, respectively.
The aqueous solution containing at least one hygroscopic substance is combined with thickeners and humectants in various concentrations to provide desired viscosity if needed in production processes. Such thickeners and humectants as well as respective concentrations are well known to a person skilled in the art.
In addition to said aqueous solution containing at least one hygroscopic substance, further textile auxiliary chemicals are added to and dissolved in the liquid ozone booster in any combination and concentration: this applies to antibackstaining agents, antifoaming agents, antimigration agents, colorants, dispersants, leveling agents, optical brighteners, silicones, softeners, stabilizers, surfactants, thickening agents, tinting agents and wetting agents.
The said treated garment is ozonized after drying/dwelling or storage for several hours, respectively.
A raw denim garment was abraded by laser or hand sanding to mark specific used look areas. Subsequently said inventive aqueous solution containing at least one hygroscopic substance was sprayed or applied by brush or sponge on the abraded areas and then subjected to ozone treatment.
A raw denim garment was desized and dried. Subsequently an aqueous solution containing at least one hygroscopic substance was sprayed or applied by brush or sponge on the abraded areas.
A raw denim garment is used as it is, or desized, and/or stonewashed or enzyme washed and/or bleached if desired and dried. Subsequently an aqueous solution containing at least one hygroscopic substance is sprayed or applied by brush or sponge or towel on specific areas of the garment.
The color changing effect in such pretreated denim fabrics is then generated by the action of ozone.
Table 1 depicts compositions of aqueous solutions which were applied to denim garments.
A raw denim fabric is used as it is, or desized, and/or stonewashed or enzyme washed and/or bleached if desired and dried. Subsequently said aqueous solution containing at least one hygroscopic substance is sprayed or applied by brush or sponge or towel on specific areas of the garment. The treated fabric is then ozonized after drying or storage for several hours, respectively, in continuous machinery set up. Afterwards the fabric is laser-treated in continuous machinery set up and washed and dried.

DMSO together with other substances representing thickeners and humectants were tested as shown in Table 1. Water plus thickener was used as a control and reference experiment. ΔL values were measured against the untreated part of the fabric in the middle of each sample (c.f. Fig. 1).

Table 1. Additives tested for the aqueous ozone booster.

Sample	Water [%]	DMSO [%]	Glycerol [%]	Xanthan gum [%]	pH	ΔL value	2 hrs drying	ΔL value freshly sprayed
Control	99.75	0	0	0.25	7.0	-0.72	2.64
1	60.00	40	0	0	8.5	6.60	3.72
2	30.00	70	0	0	9.0	5.18	2.26
3	59.75	40	0	0.25	8.5	7.40	1.48
4	58.75	40	1	0.25	8.5	5.34	2.60

The effect of boosting the ozone bleaching intensity is shown in Fig. 1 for samples 1-4 including the control sample (pure water + thickener). Samples were treated with ozone for 6 min at room temperature; one half of the sample area was sprayed with the respective solutions as shown in Table 1 and allowed to dwell/hang for two hours at ambient conditions. The other half was freshly sprayed before ozonation in order to compare the bleaching effect to the respective aged sample.
It can be seen that there was no effect after 2 hours in case of the control sample (water + thickener) due to drying-out. This was expected and clearly demonstrates the need for a better solution in order to solve the industrial problem. Only in case of the aqueous solution containing DMSO representing a very hygroscopic substance as an additive a bleaching effect was observed even after 2 hours.
In one embodiment of the invention the aqueous DMSO solution is sprayed on the denim garment on the desired selected areas (= local bleach) or the whole garment. The garment is then allowed to stand/dwell under ambient conditions for several hours simulating industrial process streams and waiting periods. The garment is then subjected to ozonation in a closed drum for a certain period of time (typically several minutes up to hours), in which the actual bleaching by ozone is taking place. Due to the wetting properties of the applied solution only pre-treated areas get locally bleached efficiently, whereas non-treated and thus dry regions undergo traditional "cleaning-up", in which comparably intense bleaching is not possible.
In Fig. 1 the results of ozone bleaching after pretreatment with samples 1-4 and thickened water as a reference are depicted.
In addition to said hygroscopic substances (for example DMSO as described above) and water, further textile auxiliary chemicals may be added to and dissolved in the liquid booster in any combination and concentration for improving the overall usability and desired performance of the product: this applies to antibackstaining agents, antifoaming agents, antimigration agents, colorants, dispersants, leveling agents, optical brighteners, silicones, softeners, stabilizers, surfactants, thickening agents, tinting agents and wetting agents. The well-known additives for experts in the field are usually applied in concentrations from 0.001 to 10 or even 20%, depending on the desired effect.

Claims

A method for increasing the color value change by increasing the lightness of dyed material comprising the following steps:
(a) applying a hygroscopic substance to said dyed material,

(b) dwelling the dyed material of step a) at least 5 minutes up to 24 hours, or even longer, and

(c) applying ozone gas to said material of (b) in order to obtain the desired change in color intensity, and wherein the ozone activity is increased by the hygroscopic substance.
The method according to claim 1, wherein the hygroscopic substance is selected from the group of hygroscopic inorganic salts, organic compounds, liquids and solvents, alcohols, dicarboxylic and carboxylic acids and deliquescent compounds, their respective anhydrates or hydrated forms, or mixtures thereof.
The method according to claim 2, wherein the hygroscopic substance is selected from the group consisting of DMSO, aluminum chloride, aluminum nitrate, calcium chloride, calcium nitrate, calcium bromide, carnallite, lithium chloride, lithium bromide, lithium iodide, lithium nitrate, lithium sulfate, magnesium chloride, magnesium nitrate, magnesium sulfate, magnesium bromide, manganese sulfate, tin sulfate, dicarboxylic acids such as malonic acid or oxalic acid, glutaric acid, urea, alpha hydroxy acids such as lactic acid, polyols as for example sorbitol, xylitol, maltitol, glycerol, sodium bromide, sodium sulfate, sodium bisulfate, sodium chloride, sodium nitrate, tachyhydrite, zinc chloride, zinc nitrate, potassium chloride, potassium nitrate, potassium sulfate, potassium bisulfate, potassium bromide, ethanol, methanol, other glycols such as ethylene/propylene/butylene glycol and respective polyglycol derivatives, or mixtures thereof.
The method according to any one of claims 1 to 3, wherein further a marker dye and/or a thickener and/or a wetting agent is applied to the dyed material in combination with the hygroscopic substance before the ozone treatment.
A method for increasing ozone activity on a dyed material comprising the steps of pre-treating said dyed material by applying a hygroscopic substance and dwelling said pre-treated dyed material at least 5 minutes up to 24 hours, or even longer, before ozone treatment.
The method of claims 1 or 5, wherein ozone activity is increased in selected parts of the dyed material by applying the hygroscopic substance to selected parts of said dyed material.
The method of claim 1 or 5, wherein the increased ozone activity induces a distinct change of the color of the dyed material.